Automatic Swing and Radius Control System and Method for a Machine Implement

ABSTRACT

Systems and methods are provided for automatically controlling operation of an implement provided on a machine. A swing angle of an arm on which the implement is provided may be controlled by determining actual and desired swing angles, generating a swing angle error, and automatically operating actuators on the machine to align the implement along the desired swing angle. An effective radius of the implement assembly may similarly be controlled by determining actual and desired effective radii, generating a radius error, and automatically operating actuators on the machine to move the implement to the desired effective radius.

TECHNICAL FIELD

The present disclosure generally relates to systems and methods for controlling machines having implements, and more particularly to systems and methods of automatically operating machines to align implements with target positions.

BACKGROUND

Machines such as, for example, backhoes, excavators, dozers, loaders, motor graders, and other types of heavy equipment use multiple actuators supplied with hydraulic fluid from an engine-driven pump to accomplish a variety of tasks. The actuators (e.g., hydraulic cylinders and motors) are used to move linkage members and implements on the machines including, for example, a boom, a stick, and a bucket. An operator controls movements of the actuators by moving one or more input devices, for example joysticks. Joystick movement manipulates a control valve associated with each actuator to control movement of the boom and stick to position or orient the bucket to perform a task. Typical operator control permits individual controlled movement of each linkage member with a corresponding operator input device, for example, along a specific input device axis. That is, each linkage (e.g. boom, stick, and bucket) is controlled by movement along a specific input device axis of one or more joysticks.

Typical operator control suffers several drawbacks due to the complex coordination required to maneuver the implement, especially when the implement is attached to a linkage system that allows implement movement about three or more degrees of freedom. For example, when moving an implement along a predefined trajectory, the operator must continuously manipulate the joysticks to complete the task. As a result, some tasks may require a high level of skill that must be learned through experience. Even experienced operators may lack the necessary skill to precisely complete complex tasks. Further, operators of all skill levels may become inefficient due to fatigue or boredom when completing routine or repetitive tasks.

In one example of a system for controlling a machine implement, U.S. Pat. No. 6,968,264 (the '264 patent) issued to Cripps on Nov. 22, 2005 discloses a machine including a mechanical arm having a first segment, a second segment, and a tool segment. Each segment pivots about a joint and is moved by one or more actuators. The '264 patent further discloses a system for controlling the mechanical arm by defining a planned path and automatically correcting an actual path of the mechanical arm when it is detected that the actual path differs from the planned path. For example, automatic correction may overcome inefficient movement by the operator due to operator fatigue or sloppy operating commands. The planned path may be stored in a library of planned paths and may be selected based one or more of the following factors: the geometry of the mechanical arm, the planned work task of the mechanical arm, the identity of the machine to which the mechanical arm is operably connected, and an optimal or preferential path of a skilled experienced operator of the machine or mechanical arm. While the machine of the '264 patent may help ensure the mechanical arm follows a particular path, the '264 patent may be limited because it fails to simplify typical complex operator input controls used to position the mechanical arm, and may be limited to use in a selected number of predetermined implement paths.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect of the disclosure, a method is provided of automatically controlling a swing angle of an arm on a machine so that an implement coupled to the arm is positioned along a desired swing angle that intersects a target point, the machine including a swing actuator configured to rotate the arm about a swing rotational axis. The method may include determining a first actual position associated with a first reference point on the machine, determining a second actual position associated with a second reference point on the machine, determining a target position associated with the target point, determining an actual swing angle based on the first and second actual positions, determining the desired swing angle based on the first actual position and the target position, determining a swing angle error based on a difference between the actual swing angle and the desired swing angle, and automatically operating the swing actuator to reduce the swing angle error.

In another aspect of the disclosure that may be combined with any of these aspects, a system is provided for automatically controlling a swing angle of an arm provided on a machine so that an implement coupled to the arm is positioned along a desired swing angle that intersects a target point. The system may include an operator station supported for rotation about a vertical operator station axis and coupled to the arm, a swing actuator operably coupled to the operator station and configured to rotate the operator station and arm relative to a swing axis substantially coincident with the vertical operator station axis. A first reference point associated with the operator station, and a second reference point associated with the implement. The system may further include a controller operably coupled to the swing actuator and configured to determine a first actual position associated with the first reference point on the machine, determine a second actual position associated with the second reference point on the machine, determine a target position associated with the target point, determine an actual swing angle based on the first and second actual positions, determine the desired swing angle based on the first actual position and the target position, determine a swing angle error based on a difference between the actual swing angle and the desired swing angle, and automatically operate the swing actuator to reduce the swing angle error.

In another aspect of the disclosure that may be combined with any of these aspects, a method is provided of automatically controlling an effective radius of an arm linkage provided on a machine so that an implement coupled to the arm linkage is aligned with a target point, the machine including at least one arm linkage actuator configured to rotate about an arm linkage axis to adjust the effective radius of the arm linkage. The method may include determining a first actual position associated with a first reference point on the machine, determining a second actual position associated with a second reference point on the machine, determining a target position associated with the target point, determining an actual effective radius based on a distance between the first actual position and the second actual position, determining a desired effective radius based on a distance between the first actual position and the target position, determining an effective radius error based on a difference between the actual effective radius and the desired effective radius, and automatically operating the at least one arm linkage actuator to reduce the effective radius error.

In another aspect of the disclosure that may be combined with any of these aspects, a system is provided for automatically controlling an effective radius of an arm linkage provided on a machine so that an implement coupled to the arm linkage is aligned with a target point. The system may include an operator station supported for rotation about a vertical operator station axis and coupled to the arm linkage, an arm linkage actuator operably coupled to the arm linkage and configured to rotate about an arm linkage axis to adjust the effective radius of the arm linkage, a first reference point associated with the operator station, and a second reference point associated with the implement. The system may further include a controller operably coupled to the arm linkage actuator and configured to determine a first actual position associated with the first reference point, determine a second actual position associated with the second reference point, determine a target position associated with the target point, determine an actual effective radius based on a distance between the first actual position and the second actual position, determine a desired effective radius based on a distance between the first actual position and the target position, determine an effective radius error based on a difference between the actual effective radius and the desired effective radius, and automatically operate the arm linkage actuator to reduce the effective radius error

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of an exemplary machine;

FIG. 2 is a plan view of the machine of FIG. 1;

FIG. 3 is a schematic illustration of an exemplary hydraulic control system that may be used with the machine of FIG. 1;

FIG. 4 is a flowchart illustrating an exemplary method of operating the hydraulic control system of FIGS. 1-3 to perform an automatic swing mode;

FIG. 5 is a flowchart illustrating an exemplary method of operating the hydraulic control system of FIGS. 1-3 to perform an automatic locate mode.

DETAILED DESCRIPTION

Embodiments of systems and methods for controlling a machine to automatically align an implement with a target point are provided. These embodiments may automatically control a swing angle and/or an effective radius of an arm linkage provided on the machine, thereby to automatically align an implement with a target point.

FIGS. 1 and 2 illustrate an exemplary machine 10 having multiple systems and components that cooperate to accomplish a task. Machine 10 may embody a fixed or mobile machine that performs some type of operation associated with an industry such as mining, construction, farming, transportation, or any other industry known in the art. For example, machine 10 may be an earth moving machine such as an excavator (as shown), a backhoe, a track-type tractor, a loader, a motor grader, or any other earth moving machine. Machine 10 may include an implement system 12 configured to move an implement 14, a drive system 16 for propelling ground engaging units 17, a power source 18 that provides power to implement system 12 and drive system 16, and an operator station 20 for operator control of implement system 12 and drive system 16.

Power source 18 may embody an engine such as, for example, a diesel engine, a gasoline engine, a gaseous fuel-powered engine or any other type of combustion engine known in the art. It is contemplated that power source 18 may alternatively embody a non-combustion source of power such as a fuel cell, a power storage device, or another source known in the art. Power source 18 may produce a mechanical or electrical power output that may then be converted to hydraulic power for moving implement system 12.

Implement system 12 may include an arm linkage acted on by fluid actuators to move implement 14. The arm linkage of implement system 12 may be complex, for example, including three or more degrees of freedom. Specifically, the arm linkage may include a boom 22 vertically pivotal about a boom axis 24 relative to a work surface 26 by a boom actuator, such as a single, double-acting, hydraulic cylinder 28. The arm linkage may also include a stick member 30 vertically pivotal about a stick axis 32 by a stick actuator, such as a single, double-acting, hydraulic cylinder 34. A bucket or implement actuator, such as a single, double-acting, hydraulic cylinder 36, may be operatively connected between stick member 30 and implement 14 to pivot implement 14 about a substantially horizontal implement pivot axis 38. In the illustrated embodiment, the hydraulic cylinder 36 is operatively coupled to an implement linkage 37, which in turn is coupled to the implement 14. Boom 22 may be pivotally connected at one end to a frame 40 of machine 10. Stick member 30 may pivotally connect to an opposing end of boom 22 and to implement 14 by way of stick axis 32 and implement pivot axis 38. Movement of boom 22 about boom axis 24, stick member 30 about stick axis 32, and implement 14 about implement pivot axis 38 may define three degrees of freedom for implement system 12. The implement system 12 may further include a fourth degree of freedom such as lateral swing movement of implement system 12, which may be generated by a swing motor 92 that rotates the operator station 20 about a swing axis 93, which in the illustrated embodiment extends substantially vertically. The implement 14 may further include a fifth degree of freedom such as tilt angle rotation, which may be generated by an actuator, such as a single, double-acting, implement tilt cylinder 94, operatively coupled to implement 14 to pivot implement 14 about a substantially horizontal tilt axis (not shown).

Each of hydraulic cylinders 28, 34, 36, and 94 may include a tube and a piston assembly (not shown) arranged to form two separated pressure chambers. The pressure chambers may be selectively supplied with pressurized fluid and drained of the pressurized fluid to cause the piston assembly to displace within the tube, thereby changing the effective length of hydraulic cylinders 28, 34, 36, and 94. The flow rate of fluid into and out of the pressure chambers may relate to a velocity of hydraulic cylinders 28, 34, 36, and 94 while a pressure differential between the two pressure chambers may relate to a force imparted by hydraulic cylinders 28, 34, 36, and 94 on the associated linkage members. The expansion and retraction of hydraulic cylinders 28, 34, 36, and 94 may function to assist in moving implement 14.

Implement 14 may include any device used to perform a particular task such as, for example, a drill, a bucket, an auger, a blade, a shovel, a ripper, a broom, a snow blower, a cutting device, a grasping device, or any other task-performing device known in the art. Numerous different implements 14 may be attachable to machine 10 and controllable via operator station 20. Each implement 14 may be configured to perform a specialized function. For example, machine 10 may include a hydraulic drill 42 attached to implement system 12.

Operator station 20 may receive input from a machine operator indicative of a desired implement movement. Specifically, operator station 20 may include one or more operator interface devices embodied as single or multi-axis joysticks located proximal an operator seat. The operator interface devices may include, among other things, a left hand joystick 58 and a right hand joystick 60. Operator interface devices 58 and 60 may be proportional-type controllers configured to position and/or orient implement 14 by varying fluid pressure to hydraulic cylinders 28, 34, 36, and 94. For example, operator interface devices 58 and 60 may impart movement of implement 14, by moving operator interface devices 58 and 60 to the left, right, forward, backward, and/or by twisting. Additionally, each operator interface device 58 and 60 may include one or more triggers 64 and 66 (see FIG. 3), respectively, for receiving operator input. It is contemplated that different operator interface devices may alternatively or additionally be included within operator station 20 such as, for example, wheels, knobs, push-pull devices, switches, pedals, and other operator interface devices known in the art. It is further contemplated that a graphical user interface 70 may be located within operator station 20 to receive operator input. Graphical user interface 70 may include various input interfaces including, for example, drop-down menus.

As illustrated in FIG. 3, machine 10 may include a hydraulic control system 72 having a plurality of fluid components that cooperate to move implement 14. In particular, hydraulic control system 72 may include a supply line 74 configured to receive a first stream of pressurized fluid from a source 76. A boom control valve 78, a swing control valve 80, an implement linkage control valve 82, a stick control valve 84, and an implement tilt control valve 86 may be connected to receive pressurized fluid in parallel from supply line 74. Each of these control valves 78-86 may be controlled by a predetermined movement of one of the operator interface devices 58, 60 or by actuation of one of the triggers 64, 66.

Source 76 may draw fluid from one or more tanks 90 and pressurize the fluid to predetermined levels. Specifically, source 76 may embody a pumping mechanism such as a variable displacement pump, a fixed displacement pump, or any other source known in the art. For example, source 76 may include a single pump that supplies pressurized actuator and pilot fluid directed to hydraulic cylinders 28, 34, 36, and 94. Source 76 may be drivably connected to power source 18 of machine 10 by, for example, a countershaft, a belt (not shown), an electrical circuit (not shown), or in any other suitable manner. Alternatively, source 76 may be indirectly connected to power source 18 via a torque converter, a reduction gear box, or in any other suitable manner. Further, source 76 may alternatively include separate pumping mechanisms to independently supply actuator and/or pilot fluid to hydraulic cylinders 28, 34, 36, and 94, if desired.

Tank 90 may constitute a reservoir configured to hold a supply of fluid. The fluid may include, for example, a dedicated hydraulic oil, an engine lubrication oil, a transmission lubrication oil, or any other fluid known in the art. One or more hydraulic systems within machine 10 may draw fluid from and return fluid to tank 90. It is contemplated that hydraulic control system 72 may be connected to multiple separate fluid tanks or to a single tank.

Each of boom, swing, implement, stick, and tilt angle control valves 78-86 may regulate the motion of their related fluid actuators. Specifically, boom control valve 78 may have valve elements movable to control the motion of hydraulic cylinder 28 associated with boom 22; swing control valve 80 may have valve elements movable to control a swing motor 92 associated with providing rotational movement of the operator station 20; implement linkage control valve 82 may have valve elements movable to control the motion of hydraulic cylinder 36 associated with drill 42; stick control valve 84 may have valve elements movable to control the motion of hydraulic cylinder 34 associated with stick member 30; and implement tilt control valve 86 may have valve elements movable to control the motion of the hydraulic cylinder associated with the implement tilt cylinder 94. It is contemplated that a pair of double acting cylinders may be used as an alternative to swing motor 92 to provide rotational movement of implement system 12, if desired. Similarly contemplated, a motor may be used as an alternative to each hydraulic cylinder 28, 34, 36, and 94 to provide movement to implement system 12.

One or more sensors may be associated with swing motor 92 and hydraulic cylinders 28, 34, 36, and 94. More specifically, machine 10 may include a plurality of sensors for monitoring the position and/or velocity of implement system 12. For example, machine 10 may include a boom sensor 112, a swing sensor 114, an implement linkage sensor 116, a stick sensor 118, and implement tilt sensor 120. Sensors 112-120 may be any type of sensors capable of monitoring and transmitting position or velocity information of machine 10 and/or implement 14 to a controller 98. For example, sensors 112-120 may be in-cylinder displacement sensors when cylinder actuators are implemented. Alternatively, sensors 112-120 may employ joint angle sensors, for example, when motor actuators are implemented. It is also contemplated that sensors 112-120 may be sensors capable of determining velocity of an element. For example, sensors 112-120 may be angular velocity sensors. Furthermore, an additional sensor may be associated with determining a relative position of machine 10. For example, machine 10 may include a level sensor 136.

Machine 10 may include controller 98 for receiving information from various input devices and responsively transmitting output commands to control valves 78-86 of hydraulic control system 72. Controller 98 may receive signals from operator interface devices 58 and 60 via communication lines 100 and 102, respectively. Further, controller 98 may receive operator input from graphical user interface 70 via communication line 106. Controller 98 may also access a memory storage device 108 via a communication line 110 to retrieve and/or store operational control data contained in memory storage device 108. Controller 98 may further receive information from one or more sensors. For example, controller 98 may receive information from boom sensor 112 via a communication line 124, from swing sensor 114 via a communication line 126, from implement linkage sensor 116 via a communication line 128, from stick sensor 118 via a communication line 130, and from implement tilt sensor 120 via communication line 132. Additionally, controller 98 may also receive input from level sensor 136 via a communication line 138. Still further, controller 98 may receive input or data delivered wirelessly to receiver 142, which may communicate with the controller 98 via communication line 144. Output commands from the controller 98 may be delivered in any suitable manner, such as in the form of control signals, to control valves 78-86 via communication lines 146, 148, 150, 152, and 154, respectively.

Implement system 12 is operable to adjust a swing angle of the arm linkage. More specifically, as best shown in FIG. 2, boom 22 and stick member 30 are coupled to the operator station 20. The operator station 20 is rotatable about swing axis 93. Boom 22 and stick member 30 are disposed along an arm linkage axis 95 which defines a swing angle α of the arm linkage about the swing axis 93 and relative to swing reference line 96. Swing motor 92 may be operated to rotate the operator station 20 about the swing axis 93, thereby adjusting the swing angle α of the arm linkage.

Implement system 12 is further operable to adjust an effective radius of the arm linkage. More specifically, as best shown in FIG. 1, the arm linkage may have an effective radius R, defined herein as a distance from a reference point disposed on the operator station 20 to a reference point associated with the implement 14. Boom 22 and stick member 30 may be pivoted about the boom and stick axes 24, 32 to adjust the effective radius R of the arm linkage.

INDUSTRIAL APPLICABILITY

The disclosed control system may be applicable to any machine that includes operator control of a work tool by way of a plurality of different actuators. The disclosed control system may increase operational efficiency by selectively implementing automatic swing angle and effective radius control, such that overall control of the implement is simplified for the operator. For purposes of explanation, only operational control of implement system 12 with reference to drill 42 will be described in detail.

An operator may be executing a task that requires the arm linkage, and therefore the implement 14, to be disposed along a desired swing angle. While it may be possible for the operator to manually manipulate the operator interface devices 58, 60, 64, 66 as needed to complete the task, efficiency may be increased by selectively overriding the manual control and instead automatically placing the implement 14 along the desired swing angle.

A method 200 of automatically placing the arm linkage in a desired swing angle α′ is illustrated by the flowchart of FIG. 4. The method 200 may be initiated at block 202, where the controller 98 may be configured to determine an automatic swing angle signal that indicates that an automatic swing angle operator interface has been actuated. The automatic swing angle signal may be generated by a predetermined movement of one of the joysticks 58, 60 or by actuation of one of the triggers 64, 66. In some embodiments, the automatic swing angle operator interface is the left hand joystick trigger 64.

In some embodiments, the method 200 may be initiated only when the actual swing angle α is within angle limits relative to the desired swing angle α′. For example, positive and negative swing axis boundaries 170, 172 (FIG. 2), may be defined and stored by the controller 98. The method 200 may optionally require the operator to manually place the implement in an actual swing angle α that falls within the boundaries 170, 172 before permitting automatic swing angle control to be initiated.

At block 204, the controller 98 may be configured to determine an actual swing angle that indicates the current rotational position of the arm linkage about the swing axis 93. The actual swing angle α may be measured about swing axis 93 relative to swing reference line 96. In some embodiments, navigational position sensors, such as first and second GPS sensors 190, 193, may be provided so that a GPS system may be used to directly determine the actual swing angle α. The first GPS sensor 190 may be positioned at a first reference point provided on the operator station, as shown in FIG. 2. In the illustrated embodiment, the first GPS sensor 190 is coupled to the operator station 20 and is positioned along a longitudinal operator station axis 191 and proximate to a rear wall 192 of the operator station 20. The second GPS sensor 193 may be coupled to the implement 14. By identifying the locations of the first and second reference points, the actual swing angle α of the arm linkage may be determined.

At block 206, the controller 98 may be configured to determine a desired swing angle α′ for the arm linkage. The desired swing angle α′ may be associated with predetermined target point 194. The target point 194 may have a target position that can be identified using a set of reference coordinates, such as GPS coordinates. Accordingly, the desired swing angle α′ may be determined using one of the first and second reference points and the target position. For example, the first GPS sensor 190 and the reference coordinates of the target position may be used to determine the desired swing angle α′, which may be measured about the swing axis 93 relative to swing reference line 96.

At block 208, the controller 98 may be configured to determine a swing axis error. The swing axis error may be determined by computing the difference between the actual swing angle α and the desired swing angle α′. The swing angle error may be identified using any suitable expression that conveys the direction and magnitude of the difference between the actual and desired swing angles.

At block 210, the controller 98 may be configured to operate the swing motor 92 in response to the swing angle error. The controller 98 may be configured to operate the swing motor 92 in a direction that reduces the swing angle error.

At block 212, the controller 98 may be configured to operate the swing motor 92 until the swing error is reduced to substantially zero or within an acceptable range near zero. When the swing error is reduced to an acceptable level, the arm linkage will be disposed along the desired swing angle α′. At this point the operator may release the automatic swing angle operator interface to exit automatic swing angle control operation.

A method 300 of automatically adjusting effective arm linkage radius additionally may be performed prior to, subsequent to, or simultaneously with the automatic swing angle method 200 described above. More specifically, the method 300 may automatically adjust the actual effective radius R to a desired effective radius R′, as illustrated by the flowchart of FIG. 5. The method 300 may be initiated at block 302, where the controller 98 may be configured to determine an automatic radius adjust signal that indicates that an automatic radius adjust operator interface has been actuated. The automatic radius adjust signal may be generated by a predetermined movement of one of the joysticks 58, 60 or by actuation of one of the triggers 64, 66. In some embodiments, the automatic radius adjust operator interface may be the same operator interface used for the automatic swing angle method 200, such as the left hand joystick trigger 64.

In some embodiments, the method 300 may be initiated only when the actual effective radius R is within distance limits relative to the desired effective radius R′. For example, positive and negative effective radius boundaries 174, 176 (FIG. 1), may be defined and stored by the controller 98. The method 300 may optionally require the operator to manually place the arm linkage in an actual effective radius R that falls within the boundaries 174, 176 before permitting automatic radius adjust control to be initiated.

At block 304, the controller 98 may be configured to determine an actual effective radius R that indicates the current effective radius of the arm linkage along the arm linkage axis 95. The actual effective radius R may be measured by first and second reference points disposed along the arm linkage axis 95, such as the first and second GPS sensors 190, 193. By identifying the locations of the first and second reference points, the actual effective radius R of the arm linkage may be determined.

At block 306, the controller 98 may be configured to determine a desired effective radius R′ for the arm linkage. The desired effective radius R′ may be associated with predetermined target point 194, which may have a target position that can be identified using a set of reference coordinates, such as GPS coordinates. Accordingly, the desired effective radius R′ may be determined using one of the first and second reference points and the target position. For example, the first GPS sensor 190 and the reference coordinates of the target position may be used to determine the desired effective radius R′, which may be equal to the distance between the first GPS sensor 190 and the target point 194.

At block 308, the controller 98 may be configured to determine an effective radius error. The effective radius error may be determined by computing the difference between the actual effective radius R and the desired effective radius R′. The effective radius error may be identified using any suitable expression that conveys the direction and magnitude of the difference between the actual and desired effective radii.

At block 310, the controller 98 may be configured to operate one or more actuators associated with the arm linkage in response to the effective radius error. For example, the boom actuator (hydraulic cylinder 28), the stick actuator (hydraulic cylinder 34), or both, may be operated to adjust the actual effective radius R of the arm linkage.

At block 312, the controller 98 may be configured to operate the one or more actuators associated with the arm linkage until the effective radius error is reduced to substantially zero or within an acceptable range near zero. When the effective radius error is reduced to an acceptable level, the arm linkage will have the desired effective radius R′. At this point the operator may release the automatic radius adjust operator interface to exit automatic swing angle control operation. If the automatic swing angle method was previously employed, then the implement 14 should be positioned in direct alignment with the target point 194 at the conclusion of the automatic radius adjust method 300.

During the automatic radius adjust method 300, it will be appreciated that the operation of the boom and stick actuators (hydraulic cylinders 28 and 34, respectively) may cause the elevation of the implement 14 to change, which may be detrimental in certain applications. Some embodiments of the automatic radius adjust method 300, therefore, may include a sub-routine that maintains a constant elevation of the implement 14 relative to the work surface 26 as the hydraulic cylinders 28, 34 are commanded to adjust the effective radius of the arm linkage. More specifically, the method may include determining an initial elevation of the implement above the work surface at any point prior to automatically operating the at least one arm linkage actuator. The second GPS sensor 193 associated with the implement 14 may be used to determine the initial elevation. The controller 98 may further be configured to maintain the implement 14 at the initial elevation as the at least one arm linkage actuator is automatically operated.

It will be appreciated that the foregoing description provides examples of the disclosed assembly and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.

Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.

Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context. 

What is claimed is:
 1. A method of automatically controlling a swing angle of an arm on a machine so that an implement coupled to the arm is positioned along a desired swing angle that intersects a target point, the machine including a swing actuator configured to rotate the arm about a swing rotational axis, the method comprising: determining a first actual position associated with a first reference point on the machine; determining a second actual position associated with a second reference point on the machine; determining a target position associated with the target point; determining an actual swing angle based on the first and second actual positions; determining the desired swing angle based on the first actual position and the target position; determining a swing angle error based on a difference between the actual swing angle and the desired swing angle; and automatically operating the swing actuator to reduce the swing angle error.
 2. The method of claim 1, in which the first reference point comprises a first GPS sensor and the second reference point comprises a second GPS sensor, and in which the first actual position, second actual position, and target position are determined using a GPS system.
 3. The method of claim 2, in which the arm is coupled to a operator station; the first GPS sensor is coupled to the operator station and is positioned along a longitudinal operator station axis proximate to a rear wall of the operator station; and the second GPS sensor is coupled to the implement.
 4. The method of claim 3, in which the swing actuator is operably coupled to the operator station and the swing rotational axis is coaxial with a vertical operator station axis.
 5. The method of claim 1, in which the swing actuator is automatically operated until the swing angle error is substantially zero.
 6. A system for automatically controlling a swing angle of an arm provided on a machine so that an implement coupled to the arm is positioned along a desired swing angle that intersects a target point, the system comprising: an operator station supported for rotation about a vertical operator station axis and coupled to the arm; a swing actuator operably coupled to the operator station and configured to rotate the operator station and arm relative to a swing axis substantially coincident with the vertical operator station axis; a first reference point associated with the operator station; a second reference point associated with the implement; a controller operably coupled to the swing actuator and configured to: determine a first actual position associated with the first reference point on the machine; determine a second actual position associated with the second reference point on the machine; determine a target position associated with the target point; determine an actual swing angle based on the first and second actual positions; determine the desired swing angle based on the first actual position and the target position; determine a swing angle error based on a difference between the actual swing angle and the desired swing angle; and automatically operate the swing actuator to reduce the swing angle error.
 7. The system of claim 1, in which: the first reference point comprises a first GPS sensor communicatively coupled to the controller; the second reference point comprises a second GPS sensor communicatively coupled to the controller; and the controller communicates with a GPS system to determine the first actual position, second actual position, and target position.
 8. The system of claim 7, in which the first GPS sensor is coupled to the operator station and is positioned along an operator station axis proximate to a rear wall of the operator station; and the second GPS sensor is coupled to the implement.
 9. The system of claim 6, in which the controller is configured to automatically operate the swing actuator until the swing angle error is substantially zero.
 10. A method of automatically controlling an effective radius of an arm linkage provided on a machine so that an implement coupled to the arm linkage is aligned with a target point, the machine including at least one arm linkage actuator configured to rotate about an arm linkage axis to adjust the effective radius of the arm linkage, the method comprising: determining a first actual position associated with a first reference point on the machine; determining a second actual position associated with a second reference point on the machine; determining a target position associated with the target point; determining an actual effective radius based on a distance between the first actual position and the second actual position; determining a desired effective radius based on a distance between the first actual position and the target position; determining an effective radius error based on a difference between the actual effective radius and the desired effective radius; and automatically operating the at least one arm linkage actuator to reduce the effective radius error.
 11. The method of claim 10, in which the first reference point comprises a first GPS sensor and the second reference point comprises a second GPS sensor, and in which the first actual position, second actual position, and target position are determined using a GPS system.
 12. The method of claim 11, in which: the arm is coupled to a operator station; the first GPS sensor is coupled to the operator station and is positioned along a longitudinal operator station axis proximate to a rear wall of the operator station; and the second GPS sensor is coupled to the implement.
 13. The method of claim 12, in which: the arm linkage includes a boom pivotably coupled to the operator station and supported for rotation about a boom axis, and a stick pivotably coupled to the boom and supported for rotation about a stick axis; the machine includes a boom actuator operably coupled to the boom and a stick actuator operably coupled to the stick; the arm linkage axis comprises at least one of the boom axis and the stick axis; and the arm linkage actuator comprises at least one of the boom actuator and the stick actuator.
 14. The method of claim 13, further comprising: determining an initial elevation of the implement above a work surface prior to automatically operating the at least one arm linkage actuator; and maintaining the implement at the initial elevation as the at least one arm linkage actuator is automatically operated.
 15. The method of claim 10, in which the at least one arm linkage actuator is automatically operated until the effective radius error is substantially zero.
 16. A system for automatically controlling an effective radius of an arm linkage provided on a machine so that an implement coupled to the arm linkage is aligned with a target point, the system comprising: an operator station supported for rotation about a vertical operator station axis and coupled to the arm linkage; an arm linkage actuator operably coupled to the arm linkage and configured to rotate about an arm linkage axis to adjust the effective radius of the arm linkage; a first reference point associated with the operator station; a second reference point associated with the implement; a controller operably coupled to the arm linkage actuator and configured to: determine a first actual position associated with the first reference point; determine a second actual position associated with the second reference point; determine a target position associated with the target point; determine an actual effective radius based on a distance between the first actual position and the second actual position; determine a desired effective radius based on a distance between the first actual position and the target position; determine an effective radius error based on a difference between the actual effective radius and the desired effective radius; and automatically operate the arm linkage actuator to reduce the effective radius error.
 17. The system of claim 16, in which: the first reference point comprises a first GPS sensor communicatively coupled to the controller; the second reference point comprises a second GPS sensor communicatively coupled to the controller; and the controller communicates with a GPS system to determine the first actual position, second actual position, and target position.
 18. The system of claim 17, in which the first GPS sensor is coupled to the operator station and is positioned along an operator station axis proximate to a rear wall of the operator station; and the second GPS sensor is coupled to the implement.
 19. The system of claim 18, in which: the arm linkage includes a boom pivotably coupled to the operator station and supported for rotation about a boom axis, and a stick pivotably coupled to the boom and supported for rotation about a stick axis; a boom actuator is operably coupled to the boom; a stick actuator is operably coupled to the stick; the arm linkage axis comprises at least one of the boom axis and the stick axis; and the arm linkage actuator comprises at least one of the boom actuator and the stick actuator.
 20. The system of claim 13, in which the controller is further configured to: determine an initial elevation of the implement above a work surface prior to automatically operating the at least one arm linkage actuator; and maintain the implement at the initial elevation as the at least one arm linkage actuator is automatically operated.
 21. The system of claim 16, in which the controller is configured to automatically operate the arm linkage actuator until the effective radius error is substantially zero. 